European patent publication 0,688,948 discloses a carburetor having an intake channel arranged in a carburetor housing. A throttle valve is provided in the intake channel and is attached to a throttle flap shaft. A mixture chamber is formed in the housing and is connected via a fuel input channel to a fuel chamber. An air intake channel connects the section of the intake channel, which is disposed upstream of the throttle flap, and functions to guide the air and mix the same with fuel in the mixture chamber. The outlet channel connects the mixture chamber to the intake channel downstream of the throttle flap so that an air/fuel mixture from the mixture chamber reaches the intake channel if, on the one hand, a valve for the ancillary channel, and, on the other hand, a valve for the air/fuel mixture are brought into a corresponding open position. These valve means include a rotating disc valve as well as a needle valve having functions which must be precisely matched to each other. However, considerable complexity with respect to structure results for the proper function.
German patent publication 195 04 400 discloses a carburetor for an internal combustion engine. An intake channel having a throttle flap is provided in the housing of this carburetor. The throttle flap is mounted in the intake channel so as to be pivotally journalled. A control chamber, which is filled with fuel, is connected via a main fuel channel and an idle fuel channel to the intake channel. Furthermore, a shunt channel is provided via which an additional quantity of air/fuel mixture can be supplied to the intake channel downstream of the throttle flap when starting.